High-pressure metal-vapor electric discharge device



Sept. 17, 1940- J.W. RYDE 2,215,300

HIGHYRE-SSURE METAL-VAPDR ELECTRIC DISCHARGE DEVICE Filed July 26, 1939INVENTOR John W]? de BY 6M TORNEY Patented Sept. 17, 1940 UNITED STATESPATENT OFFICE HIGH-PRESSURE METAL-VAPOR ELECTRIC DISCHARGE DEVICE JohnW. Ryde, Wembley, England, assignor to General Electric Company, acorporation of New York Application July 26, 1939, Serial No. 286,697 InGreat Britain July 29, 1938 2 Claims.

This invention relates to high-pressure metalvapor electric dischargedevices of the type wherein, in full operation, the pressure of thevapor exceeds five atmospheres and the distance between the terminationsof the discharge path is much less than any internal dimension of theenvelope in a plane perpendicular to and passing through the straightline joining the said terminations. It relates also totheir'manufacture.

Devices of this type may burst in operation under abnormal conditions.It is easy to make the main part of the envelope strong enough to standthe internal pressure so long as it is in its original state; butconvection currents playing on it are apt to devitrify or otherwiseweaken it.

Damage by convection streams could be prevented by providing shieldswhich disperse the streams and prevent them impinging on the envelope.The shields might be of the same material as the envelope and thereforebe damaged by the streams incident on them; but this damage would notmatter, since the shields are subject to little stress and can be placedout of the path of the useful light. On the other hand, it is difiicultto provide adequate shields; for they are to be introduced throughapertures in the envelope; if these apertures are wide enough to admitthe shields, they may themselves introduce weakness.

The object of this invention is to provide shields that can beintroduced through narrow apertures in the envelope subsequently filled,for example, by the seals carrying the leading-in-conductors and thatyet protect the envelope sufllciently. Another object of the inventionis to provide a method of manufacture for lamps of the above type. Stillfurther objects and advantages attaching to the device and to its useand operation will be apparent to those skilled in the art from thefollowing particular description.

According to the invention a device of the type specified comprises oneor more strips of vitreous material, of substantially the same coemcientof thermal expansipn as the envelope, fused to the envelope and locatedso that, in some position (not necessarily or preferably all positions)of the device, they lie above the line between the terminations of thedischarge path. A strip may be fused to the envelope at its edges orcorners; or beads or the like may be inserted between the envelope andthe strip, fused on one side to the envelope and on the other to thestrip.

The strips can be introduced lengthwise through a narrow aperture,guided into position and fixed thereby heating the envelope where theyrest on it. Several strips may be thus arranged side by side and/or endto end, so that they make up a continuous shield of area greater thanthat of any single strip. Again several isolated strips, or combinationsof strips, may be provided at different parts of the envelope, so as toreceive the convection streams when the lamp is operated in differentpositions. The strips must not be so close to thedischarge path thatthey are raised to a temperature at which they evaporate appreciably.

In the drawing accompanying and forming part of this specification anembodiment of the invention is shown in a side elevational, partlysectional view. The lamp illustrated in the drawing is capable ofdissipating 500 watts during operation and comprises a sphericalenvelope l of quartz, for example, having an internal diameter of about40 mm. and a wall thickness of about 3 mm. The thermionic electrodes 2,2 lie along a diameter and are spaced 5 mm. apart symmetrically aboutthe centre. The apertures, finally closed by the seals 3, 3 carrying themain electrodes, were originally 8 mm. in diameter. Each shield 4 or 5consists of a strip of quartz of approximately 8 x 25 x 1.5 mm.,introduced through one of these apertures. A single strip of this kindis usually sufficient to protect the envelope from the convectionstreams in any one position of the lamp; but two shields mounted end toend are sometimes preferable. Strips 4 and 5 are in mutuallyperpendicular planes, so that the lamp can be operated in two positionsdiflering in rotation through a right angle about a diameter of theenvelope. The strips are fixed to the envelope at their corners byfusion.

The envelope tcontains a starting gas, such as argon or neon, and aquantity of mercury in an amount such that the lamp is capable ofoperation with a mercury vapor pressure inexcess of five atmospheres.

While I have shown and described and have pointed out in the annexedclaims certain novel features of the invention, it will be understoodthat various omissions, substitutions and changes in the forms anddetails of the device illustrated and in its use and operation may bemade by those skilled in the art without departing from the broad spiritand scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

l. A gaseous electric discharge lamp comprising a generally sphericalcontainer which is constituted of vitreous material and which enclosesspaced electrodes, said' container having in the wall thereof an openingof a diameter which is only a minor fraction 01' the diameter of thecontainer itself, a lead-in conductor for one 01' said electrodesextending through the opening and supported therein by a body ofvitreous material which completely closes the opening, a quantity of anionizable medium in the container in an amount such that the lamp iscapable of operation with an internal pressure of at least severalatmospheres, and a narrow strip oi vitreous material mounted in thecontainer substantially parallel to and oi'i'set from a straight linedrawn between the said electrodes for preventing devitriflcation-oi theportion of the container subtendedbythestrimthesaidstripbeingofsuchlimited dimensions that it is capableof being introduced into the container through the said wall openingprior to sealing the said closure body therein.

2. A gaseous electric discharge lamp comprising a generally sphericalcontainer which is constituted of vitreous material and which enclosesspaced electrodes, said container having in thewallthereoianopeningoiadiameterwhichis only a minor traction of thediameter of the container itself, a lead-in conductor for one or saidelectrodes extending through the opening and supported therein by a body0! vitreous material which completely closes the opening, a quantity ofan ionizable metal in the container in an amount such that the lamp iscapable or operation with an internal pressure of at least fiveatmospheres, and a substantially planar strip of vitreous material fusedat its extremities to the inner wall oi the container so that theportion of the container subtended by the strip is shielded fromconvection currents occurring in the gaseous atmosphere of the lampduring operation thereof, the said strip beingoisuchlimiteddimensionsthatitiscapabie 01! being introduced into the containerthrough thesaidwallopeningpriortosealingthesaid closure body therein andhaving approximately the same coemcient of expansion as the material ofsaid container.

JOHN W. RYDI.

